Structurally diverse 1,2-diarylpropanes from the fruit of Crataegus pinnatifida and the investigation on their mirror-image ECD spectra with the same absolute configurations

• Published in: Phytochemistry (Oxford) 2024-06, Vol.222, p.114067-114067, Article 114067
• Main Authors: Lv, Tian-Ming, Guo, Rui, Yang, Bo-Han, Zhao, Peng, Lin, Bin, Huang, Xiao-Xiao, Song, Shao-Jiang
• Format: Article
• Language: English
• Subjects: 1,2-diarylpropanes; Chiral separation; Crataegus pinnatifida; Rosaceae; The flipping of the ECD curves
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2024.114067

1,2-diarylpropanes are a kind of abundant natural products formed by radical coupling. On account of molecular flexibility, it was challenged in the identifications of relative and absolute configurations of the 1,2-diarylpropanes. In this research, fourteen pairs of enantiomeric 1,2-diarylpropanes (1a/1b-14a/14b), comprising twelve previously undescribed pairs (1a/1b-4a/4b, 6a/6b-10a/10b, and 12a/12b-14a/14b), were isolated from the fruit of Crataegus pinnatifida. Their structures were determined through multiple NMR spectral analyses, empirical NMR rules, X-ray crystallography, and the comparison of experimental ECD spectra with calculated data. In addition, the analysis of ECD spectra revealed that substituent effects could generate an inverted chiroptical response, exhibiting in mirror-image ECD signals. This phenomenon was investigated by conformational analysis, molecular orbital analysis, the transition density matrix and hole/electron distributions. Moreover, a potential experimental rule was proposed for the rapid determination of the absolute configurations of the 1,2-diarylpropanes. [Display omitted] •Twelve undescribed pairs of enantiomeric 1,2-diarylpropanes were isolated.•The phenomenon of ECD inversion was investigated.•A rule was proposed for the determination of the absolute configurations.